[wvxvw]

А зачем в хелп смотреть, если это на поверхности плавает?

    public function watchXML(xml:Object, notifiable:IXMLNotifiable, uid:String = null):void
    {
        if ((xml is XMLList) && xml.length() > 1)
        {
            for each(var item:Object in xml)
            {
                watchXML(item, notifiable, uid);
            }
        }
        else
        {
            // An XMLList object behaves like XML when it contains one
            // XML object.  Casting to an XML object is necessary to
            // access the notification() function.
            var xmlItem:XML = XML(xml);
 
            // First make sure the xml node has a notification function.
            var watcherFunction:Object = xmlItem.notification();
 
            if (!(watcherFunction is Function))
            {
                watcherFunction = initializeXMLForNotification();
                xmlItem.setNotification(watcherFunction as Function);
                if (uid && watcherFunction["uid"] == null)
                    watcherFunction["uid"] = uid;
            }
 
            // Watch lists are maintained on the notification function.
            var xmlWatchers:Dictionary;
            if (watcherFunction["watched"] == undefined)
                watcherFunction["watched"] = xmlWatchers = new Dictionary(true);
            else
                xmlWatchers = watcherFunction["watched"];
 
            xmlWatchers[notifiable] = true;
        }
    }

И, ей богу, сделайте лучше сами, чем этим пользоваться.